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DOPPLER SONAR SYSTEMS FOR BERTHING AND NAVIGATION

A new digital system developed by Sadelec operates on the principles of the Doppler effect; it can be used to calculate the longitudinal distance covered with respect to the sea bottom during a given period and the angle between the speed vector and the longitudinal axis of the ship. The speed components can be determined at depths up to 150 m; beyond this depth, measurements are obtained by reverberations from stable layers 20 m below the ship. The working frequency is 300 kc/sec/ Two vertically symmetrical emission bands are used to ensure precision. The ultrasonic emissions are not made directly in the water, and the measurements are therefore not affected by temperature or stability. The system is also useful in docking operations.